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Abstract:

A tiled display apparatus includes at least five functionally identical
transparent partially-overlapped display tiles arranged in two
dimensions, each display tile including pixels arranged in a
two-dimensional array, and the display tiles being disposed so that light
emitted by pixels located beneath a neighboring display tile at the edge
of the pixel array passes through the neighboring display tile.

Claims:

1. A tiled display apparatus, comprising: at least five functionally
identical transparent partially-overlapped display tiles arranged in two
dimensions, each display tile including pixels arranged in a
two-dimensional array, and the display tiles being disposed so that light
emitted by pixels located beneath a neighboring display tile at the edge
of the pixel array passes through the neighboring display tile.

2. A tiled electro-luminescent display apparatus, comprising:(a) a
plurality of display tiles arranged in a regular two-dimensional array,
each display tile including:i) a transparent flexible substrate and a
transparent flexible cover affixed to the transparent flexible
substrate;ii) a first electrode formed over the transparent flexible
substrate, one or more layers of light-emitting material formed over the
first electrode, and a second electrode formed over the one or more
layers of light-emitting material;iii) wherein the first or second
electrode forms independently-controllable light-emitting pixels arranged
in rows and columns of a regular, two-dimensional, four-sided pixel array
defining a display area, the pixel array having first edge pixels located
on the edge of a first side of the pixel array, second edge pixels
located on the edge of a second side of the pixel array opposite the
first side, third edge pixels located on the edge of a third side of the
pixel array adjacent to the first and second sides, and fourth edge
pixels located on the edge of a fourth side of the pixel array opposite
the third side and adjacent to the first and second sides, each pixel
separated from a neighboring pixel by a respective inter-pixel distance
in each of the two dimensions;iv) wherein the transparent flexible
substrate or transparent flexible cover extends beyond the pixel array on
all four sides of the pixel array a distance greater than the inter-pixel
distance in the respective dimensions, the transparent flexible substrate
or transparent flexible cover extensions defining a first transparent
tile area on the first side of the pixel array, a second tile area on the
second side of the pixel array opposite the first side, a third
transparent tile area on the third side of the pixel array adjacent to
the first and second sides, a fourth tile area on the fourth side of the
pixel array opposite the third side and adjacent to the first and second
sides; andv) wherein the first, second, third and fourth tile areas do
not include pixels; and(b) wherein the display tiles are arranged so
that:i) the first transparent tile area of each display tile is disposed
above the second tile area of a first neighboring display tile so that
light emitted from the second edge pixels of the first neighboring
display tile is transmitted through the first transparent tile area,ii)
the second tile area of each display tile is disposed below the first
tile area of a second neighboring display tile so that light emitted from
the second edge pixels is transmitted through the first transparent tile
area of the second neighboring tile;iii) the third transparent tile area
of each display tile is disposed above the fourth tile area of a third
neighboring display tile so that light emitted from the fourth edge
pixels of the third neighboring display tile is transmitted through the
third transparent tile area; andiv) the fourth tile area of each display
tile is disposed below the third transparent tile area of a fourth
neighboring display tile so that light emitted from the fourth edge
pixels is transmitted through the third transparent tile area of the
fourth neighboring tile; andv) wherein the pixels in the pixel arrays of
each display tile and the neighboring display tiles do not overlap, form
a regular, two-dimensional pixel array, and are separated by the
respective inter-pixel distances in each of the dimensions.

3. The tiled electro-luminescent display apparatus of claim 1, further
including a black matrix material formed on the transparent flexible
substrate or transparent flexible cover in the first transparent, second,
third transparent or fourth tile areas of one or more display tiles.

4. The tiled electro-luminescent display apparatus of claim 1, wherein the
transparent flexible substrate or transparent flexible cover has a
vertical edge, and further including a black matrix material located on
the vertical edge of the transparent flexible substrate or transparent
flexible cover.

5. The tiled electro-luminescent display apparatus of claim 1, wherein the
first transparent tile area or the third transparent tile area has a
vertical edge that is located laterally between two pixels on the
corresponding neighboring tile.

6. The tiled electro-luminescent display apparatus of claim 1,a) wherein
the second and fourth display tile areas are larger than the first and
third transparent tile areas, respectively; andb) the first or second
electrode has an extended electrode portion extending a distance greater
than the corresponding inter-pixel distance into the second or fourth
tile area, and the first or second electrode does not extend a distance
greater than the corresponding inter-pixel distance into the
corresponding first or third transparent tile area.

7. The tiled electro-luminescent display apparatus of claim 6, wherein at
least a portion of the second tile area is disposed beneath the pixel
array of the second neighboring display tile.

8. The tiled electro-luminescent display apparatus of claim 6, further
including one or more display tile controller(s) located on the second or
fourth tiles areas of one or more display tiles, the one or more display
tile controller(s) being connected to the first or second electrodes of
the corresponding display tile(s).

9. The tiled electro-luminescent display apparatus of claim 8, wherein the
one or more display tile controller(s) are chiplets having separate
substrates independent of the transparent flexible substrate or
transparent flexible cover of the display tile(s).

10. The tiled electro-luminescent display apparatus of claim 8, wherein
the display tile controller(s) are electrically connected to the display
tile controller(s) of a neighboring tile with a communication buss.

11. The tiled electro-luminescent display apparatus of claim 8, wherein
the one or more display tile controller(s) are passive-matrix
controller(s) and the pixel array is controlled as a passive-matrix pixel
array.

12. The tiled electro-luminescent display apparatus of claim 1, further
including fifth and sixth neighboring display tiles and wherein:a) the
first transparent tile area of the third neighboring display tile is
disposed above the second tile area of the fifth neighboring display tile
so that light emitted from the second edge pixels of the fifth
neighboring display tile is transmitted through the first transparent
tile area of the third neighboring display tile,b) the third transparent
tile area of the first neighboring display tile is disposed above the
fourth the area of the fifth neighboring display tile so that light
emitted from the fourth edge pixels of the fifth neighboring display tile
is transmitted through the third transparent tile area of the first
neighboring tile;c) the first transparent tile area of the sixth
neighboring display tile is disposed above the second tile area of the
third neighboring display tile so that light emitted from the second edge
pixels of the third neighboring display tile is transmitted through the
first transparent tile area of the sixth neighboring display tile,d) the
third transparent tile area of the second neighboring display tile is
disposed above the fourth tile area of the sixth neighboring display tile
so that light emitted from the fourth edge pixels of the sixth
neighboring display tile is transmitted through the third transparent
tile area of the second neighboring tile; ande) wherein the pixels in the
pixel arrays of the display tile and the fifth, sixth, third, and first
neighboring display tiles do not overlap, form a regular, two-dimensional
pixel array, and are separated by the respective inter-pixel distances in
each of the dimensions.

13. The tiled electro-luminescent display apparatus of claim 12, wherein
the fifth, third, and sixth neighboring display tiles are offset
laterally with respect to the first and second neighboring display tiles.

14. The tiled electro-luminescent display apparatus of claim 1, wherein
each display tile has a first flat portion located above the second tile
area of the first neighboring display tile, a curved portion in the
display area, and a second flat portion in the second tile area, the
second flat portion being adjacent to, and in a common plane with, a
second flat portion of the second tile area of the first neighboring
display tile.

15. The tiled electro-luminescent display apparatus of claim 1, wherein
the transparent flexible substrate and transparent flexible cover of one
or more display tile(s) have respective edges and wherein the edges are
jagged or stepped.

16. The tiled electro-luminescent display apparatus of claim 1, wherein
the transparent flexible substrate and transparent flexible cover of the
display tiles have respective edges and wherein the transparent flexible
substrate and transparent flexible cover of the display tiles have
different sizes so that the transparent flexible substrate extends beyond
the edge of the transparent flexible cover, or the transparent flexible
cover extends beyond the edge of the transparent flexible substrate, on
one or more sides.

17. The tiled electro-luminescent display apparatus of claim 1, wherein
the transparent flexible substrate or transparent flexible cover has a
thickness equal to or less than the inter-pixel distance in one or both
dimensions.

18. The tiled electro-luminescent display apparatus of claim 1, wherein
the pixels have sizes in one or more dimensions and either or both of the
transparent flexible substrate or transparent flexible cover has a
thickness equal to or less than the pixel width in at least one
dimension.

19. The tiled electro-luminescent display apparatus of claim 1, further
comprising an emitted-light-diffusing element optically integrated with
the one or more layers of light-emitting material.

20. The tiled electro-luminescent display apparatus of claim 1, further
comprising an array of color filters located in correspondence with the
pixels and a black matrix located between the color filters, and wherein
the one or more layers of light-emitting material emit white light to
form a full-color tiled display.

Description:

FIELD OF THE INVENTION

[0001]The present invention relates to flat-panel display apparatus having
a plurality of display tiles that each includes a flexible substrate.

BACKGROUND OF THE INVENTION

[0002]Flat-panel display devices are widely used in conjunction with
computing devices, in portable electronic devices, and for entertainment
devices such as televisions. Such flat-panel displays typically employ a
plurality of pixels distributed over a substrate to display images. Each
pixel incorporates several, differently colored light-emitting elements
commonly referred to as sub-pixels, typically emitting red, green, and
blue light, to represent each image element. Pixels and sub-pixels are
not distinguished herein; all light-emitting elements are called pixels.
A variety of flat-panel display technologies are known, for example
plasma displays, liquid crystal displays, and light-emitting diode
displays.

[0003]Light-emitting diodes (LEDs) incorporating thin films of
light-emitting materials forming light-emitting elements have many
advantages in a flat-panel display device and are useful in optical
systems. One exemplary organic LED display device includes an array of
organic LED light-emitting elements. Alternatively, inorganic materials
can he employed and can include phosphorescent crystals or quantum dots
in a polycrystalline semiconductor matrix. Other thin films of organic or
inorganic materials can also be employed to control charge injection,
charge transport, or charge blocking to the light-emitting-thin-film
materials, and are known in the art. The thin-film materials are placed
upon a-substrate between electrodes, with an encapsulating cover layer or
plate. Light is emitted from a pixel when current supplied by the
electrodes passes through the light-emitting material. The frequency of
the emitted light is dependent on the nature of the material used. In
such a display, light can be emitted through the substrate (a bottom
emitter) or through the encapsulating cover (a top emitter), or both.

[0004]LED devices can include a patterned light-emissive layer wherein
different materials are employed in the pattern to emit different colors
of light when current passes through the materials. Alternatively, one
can employ a single emissive layer, for example, a white-light emitter,
together with color filters for forming a full-color display. It is also
known to employ a white light-emitting element that does not include a
color filter. A design employing an unpatterned white-light emitter has
been described together with a four-color pixel comprising red, green,
and blue color filters and sub-pixels and an unfiltered white sub-pixel
to improve the efficiency of the device.

[0005]Typical display apparatuses range in size from small displays used
in mobile devices to very large displays visible to thousands of viewers.
Large displays can be provided by tiling smaller display devices
together. For example, video walls using multiple video displays are
frequently seen in the electronic media and flat-panel displays can be
tiled to create larger displays. Multiple projector systems used to
create a large, tiled, high-resolution display are also known.

[0006]Flat-panel tiled displays are well known in the prior art. Many
flat-panel tiled display apparatuses employ rectangular display tiles
with pixel arrays formed in display areas on the display tile. Each
display tile has a separate substrate that is butted together at the
edges with a separate display tile to form a single, flat surface. In
such a configuration, it is important that the edge seams between the
display tiles be imperceptible to a viewer and therefore do not have a
reflectance or light emission that differs from the display area of the
display tiles. Moreover, the gap between adjacent light-emitting pixels
is the same over the butted tiled edges as it is between light-emitting
pixels in the display area so that the pixels are uniformly distributed
over the tiled array.

[0007]Various butted tiling methods employ tile structures fastened
together into an array with the use of a frame or an electroluminescent
display panel including multiple small-size panels secured to a larger
support with an intervening adhesive layer. Alternatively, tiled display
structures can include a plurality of display tiles mounted upon a back
panel that are interconnected through electrical stand-off connectors or
that include a plurality of display tiles mounted upon a back panel with
electrode segments formed over electrode busses. Tiles attached to a
mounting surface can emit light from one surface of the tile and
conductors can be connected at a second surface. It is also known to use
black-matrix material in a tiled display. A tiled display can locate all
of the electronic circuitry beneath the pixel array. Vertical
interconnects arc made between the pixel electrodes and drive circuits,
thereby enabling a seamless image. Optical structure that hide tile seams
are also known in the art, for example by employing a distributed
ultra-low magnification fly's-eye optical system integrated with the
display tiles, effectively excluding and obscuring an image of the tile
seams.

[0008]Generally, prior art methods for obscuring tile seams seek to reduce
the tile perimeter width so that butted-together tiles have a common
inter-pixel distance over the multiple tiles. In other approaches, the
tile seam is made less visible, for example through optical structures,
by controlling the pixels in the display tiles, or employing special tile
cutting or encapsulation techniques. Other disclosures seek to ensure
that the power distribution over the tiles is uniform.

[0009]It is difficult and expensive, however, to maintain a constant
inter-pixel distance across the edge of two butted-together tiles. In
particular, OLED devices require protection from environmental
contamination, especially moisture. To avoid such contamination, OLED
devices generally employ a hermetic seal around the perimeter of the
display. This hermetic seal can cause the edge of a tile to be wider than
the inter-pixel distance.

[0010]Another technique for reducing tile seam visibility relies on
overlapping the display tiles. For example, U.S. Patent Publication
2006/0108915, now abandoned, discloses a tiled OLED display structure
wherein OLED display tiles are stacked over non-display areas of other
OLED display-tile substrates. Commonly-assigned U.S. Pat. No. 6,614,171
discloses a tiled display having tiles with spaced-apart edge pixels
stacked upon a back-plate that includes pixels disposed between the
spaced-apart display tile edge pixels. These structures employ multiple
substrates, are not readily scalable, and are difficult to interconnect.
Alternatively, WO2006023901 discloses an array of display tiles for which
the edge seam width is reduced by overlapping the edge of the tiles so
that a ribbon cable connector can extend beneath the overlap. Another
approach is described in WO 2003/042966 and U.S. Pat. No. 7,362,046. This
method uses a complex support structure and a plurality of printed
circuit boards, on each of which is mounted a separate display with a
separate substrate. The printed circuit boards are mounted at an angle to
a viewing surface and the edge of each printed circuit board overlaps the
edge of a neighboring printed circuit board. In a related disclosure,
commonly assigned, co-pending U.S. Patent Publication 2007/0001927
describes an electronic signage system having a plurality of display
elements wherein one display element overlaps another display element.
These designs can overlap the tile edge of one tile with a neighboring
tile, thereby reducing the tile seam width by one half. However, this
reduction can be inadequate, especially for high-resolution displays with
small inter-pixel distances, and still restricts the edge width of the
display tiles. U.S. Patent Application 2009/0021162 describes a flexible
emissive display that can include display tiles coupled to a flexible
support but does not thereby reduce tile seam visibility.

[0011]There is a need, therefore, for an improved tiled display apparatus
that overcomes the problems noted above.

SUMMARY OF THE INVENTION

[0012]In accordance with the present invention, there is provided a tiled
display apparatus comprising: at least five functionally identical
transparent partially-overlapped display tiles arranged in two
dimensions, each display tile including pixels arranged in a
two-dimensional array, and the display tiles being disposed so that light
emitted by pixels at the edge of the pixel array passes through a
neighboring display tile.

[0013]In accordance with another aspect of the present invention there is
provided a tiled electro-luminescent display apparatus, comprising:

[0014](a) a plurality of display tiles arranged in a regular
two-dimensional array, each display tile including: [0015]i) a
transparent flexible substrate and a transparent flexible cover affixed
to the transparent flexible substrate; [0016]ii) a first electrode formed
over the transparent flexible substrate, one or more layers of
light-emitting material formed over the first electrode, and a second
electrode formed over the one or more layers of light-emitting material;
[0017]iii) wherein the first or second electrode forms
independently-controllable light-emitting pixels arranged in rows and
columns of a regular, two-dimensional, four-sided pixel array defining a
display area, the pixel array having first edge pixels located on the
edge of a first side of the pixel array, second edge pixels located on
the edge of a second side of the pixel array opposite the first side,
third edge pixels located on the edge of a third side of the pixel array
adjacent to the first and second sides, and fourth edge pixels located on
the edge of a fourth side of the pixel array opposite the third side and
adjacent to the first and second sides, each pixel separated from a
neighboring pixel by a respective inter-pixel distance in each of the two
dimensions; [0018]iv) wherein the transparent flexible substrate or
transparent flexible cover extends beyond the pixel array on all four
sides of the pixel array a distance greater than the inter-pixel distance
in the respective dimensions, the transparent flexible substrate or
transparent flexible cover extensions defining a first transparent tile
area on the first side of the pixel array, a second tile area on the
second side of the pixel array opposite the first side, a third
transparent tile area on the third side of the pixel array adjacent to
the first and second sides, a fourth tile area on the fourth side of the
pixel array opposite the third side and adjacent to the first and second
sides; and [0019]v) wherein the first, second, third and fourth tile
areas do not include pixels; and

[0020](b) wherein the display tiles are arranged so that: [0021]i) the
first transparent tile area of each display tile is disposed above the
second tile area of a first neighboring display tile so that light
emitted from the second edge pixels of the first neighboring display tile
is transmitted through the first transparent tile area; [0022]ii) the
second tile area of each display tile is disposed below the first tile
area of a second neighboring display tile so that light emitted from the
second edge pixels is transmitted through the first transparent tile area
of the second neighboring tile; [0023]iii) the third transparent tile
area of each display tile is disposed above the fourth tile area of a
third neighboring display tile so that light emitted from the fourth edge
pixels of the third neighboring display tile is transmitted through the
third transparent tile area; and [0024]iv) the fourth tile area of each
display tile is disposed below the third transparent tile area of a
fourth neighboring display tile so that light emitted from the fourth
edge pixels is transmitted through the third transparent tile area of the
fourth neighboring tile; and [0025]v) wherein the pixels in the pixel
arrays of each display tile and the neighboring display tiles do not
overlap, form a regular, two-dimensional pixel array, and are separated
by the respective inter-pixel distances in each of the dimensions.

[0026]The present invention has the advantage that a tiled display can be
arbitrarily scaled, incorporate large edge widths to suppress the ingress
of moisture or other environmental contaminants, reduce tile seams,
reduce manufacturing difficulties, provide a flexible display apparatus,
increase light output, and provide substrate space for wiring and control
circuits on the display tile substrates, thereby improving system
integration.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]The above and other objects, features, and advantages of the present
invention will become more apparent when taken in conjunction with the
following description and drawings wherein identical reference numerals
have been used, where possible, to designate identical features that are
common to the figures, and wherein:

[0028]FIG. 1 is a simplified schematic of five display tiles according to
an embodiment of the present invention;

[0029]FIG. 2 is a simplified schematic of a display tile according to an
embodiment of the present invention;

[0030]FIG. 3 is a partial cross section of an organic light-emitting diode
with a color filter useful in understanding the present invention;

[0031]FIG. 4 is a plan view of one display tile in a tiled display
according to an embodiment of the present invention;

[0032]FIG. 5 is a plan view of an alternative display tile in a tiled
display according to an embodiment of the present invention;

[0033]FIG. 6 is a plan view of two overlapping display tiles in a tiled
display according to an embodiment of the present invention;

[0034]FIG. 7 is a simplified plan view of two overlapping display tiles in
a tiled display according to an embodiment of the present invention;

[0035]FIG. 8 is a simplified plan view of four overlapping display tiles
in a tiled display according to an embodiment of the present invention;

[0036]FIG. 9 is a simplified plan view of nine overlapping display tiles
in a tiled display according to an embodiment of the present invention;

[0037]FIG. 10 is a simplified plan view of four overlapping display tiles
with offset rows in a tiled display according to an embodiment of the
present invention;

[0038]FIG. 11 is a partial cross section of the edges of two overlapping
display tiles in a tiled display according to an embodiment of the
present invention;

[0039]FIG. 12 is a partial cross section of the edges of two overlapping
display tiles in a tiled display according to an alternative embodiment
of the present invention;

[0040]FIG. 13 is a partial cross section of the edges of two overlapping
display tiles in a tiled display wherein the cover and substrate extend a
different distance over the tile edge according to an alternative
embodiment of the present invention;

[0041]FIGS. 14A and 14B are plan views of a display tile that has jagged
or stepped edges according to alternative embodiments of the present
invention; and

[0042]FIG. 15 is a partial cross section of the edges of a display tile
that includes a light-scattering layer and color filters according to an
alternative embodiment of the present invention;

[0043]FIG. 16 is two photographs of a tiled display having two display
tiles according to an embodiment of the present invention; and

[0044]FIG. 17 is a schematic of a partial tiled display having jagged
pixel edges according to an embodiment of the present invention;

[0045]FIG. 18 is a schematic of the partial tiled displays of FIG. 17 in a
tiled arrangement according to an embodiment of the present invention;
and

[0046]FIG. 19 is a partial cross section of three overlapping display
tiles in a tiled display according to one embodiment of the present
invention;

[0047]FIG. 20 is a partial cross section of the edges of two overlapping
display tiles in a tiled display according to an embodiment of the
present invention; and

[0048]FIG. 21 is a partial cross section of a display tile having a
chiplet controller according to an embodiment of the present invention.

[0049]The layers of the figures are not to scale, since the differences in
size of the elements in the figures are too great to permit depiction at
scale.

DETAILED DESCRIPTION OF THE INVENTION

[0050]In an embodiment of the present invention illustrated in FIG. 1, a
tiled display apparatus can include at least five functionally identical
transparent partially-overlapped display tiles 25, 25A, 25B, 25C, 25D,
arranged in two dimensions, each display tile 25, 25A, 25B, 25C, 25D,
including pixels arranged in a two-dimensional array 10, and the display
tiles 25, 25A, 25B, 25C, 25D being disposed so that light emitted by
pixels located beneath a neighboring display tile at the edge of the
pixel array passes through the neighboring display tile. By partially
overlapped, is meant that one or more portions, but not all, of each
display tile is disposed above or below a neighboring display tile. By
functionally identical is meant that the disposition of any the display
tiles can be interchanged with the disposition of any of the other
display tiles without operationally affecting the tiled display
apparatus. For example, display tile 25A can be interchanged with any one
of the display tiles 25, 25B, 25C, or 25D.

[0051]Referring further to FIG. 1, according to an embodiment of the
present invention, a tiled electro-luminescent display apparatus includes
a plurality of display tiles 25;25A, 25B, 25C, 25D arranged in a regular
two-dimensional array. Referring to FIG. 2, each display tile 25 includes
a pixel array 10 comprising an array of pixels 15, some of which, e.g.
pixels 15A, 15B, 15C, and 15D are located on the edge of the pixel array
10. The pixels 15A, 15B, 15C, 15D formed on the edge of the pixel array
10 are collectively referred to as edge pixels 15E. The pixels 15 are
formed on a transparent flexible substrate 22 with a transparent flexible
cover 26 affixed to the transparent flexible substrate 22. As shown in
FIG. 3, a first electrode 12 is formed over the transparent flexible
substrate 22, one or more layers 14 of light-emitting material are formed
over the first electrode 12, a second electrode 16 is formed over the one
or more layers 14 of light-emitting material, and an optional color
filter 18 filters emitted light to form a light-emitting pixel 15, 15E.
In one embodiment, illustrated in FIG. 3, the first electrode 12 is
transparent and the second electrode 16 is reflective so that emitted
light 5 passes through the first electrode 12 and substrate 22.
Alternatively, the first electrode 12 is reflective, the second electrode
16 is transparent, and light is emitted through the cover 26.

[0052]The first or second electrode 12, 16 (FIG. 3) forms
independently-controllable light-emitting pixels 15, 15E. As shown in
FIG. 2, the pixels 15, 15E are arranged in rows and columns of a regular,
two-dimensional, four-sided pixel array 10 defining a display area, the
pixel array 10 having first edge pixels 15A located on the edge of a
first side of the pixel array 10, second edge pixels 15B located on the
edge of a second side of the pixel array 10 opposite the first side,
third edge pixels 15C located on the edge of a third side of the pixel
array 10 adjacent to the first and second sides, and fourth edge pixels
15D located on the edge of a fourth side of the pixel array 10 opposite
the third side and adjacent to the first and second sides, each pixel 15,
15E separated from a neighboring pixel by an inter-pixel distance d in
each of the two dimensions. The distance d can be the same in each
dimension or can be different.

[0053]The transparent flexible substrate 22 or transparent flexible cover
26 extends beyond the pixel array 10 on all four sides of the pixel array
10 a distance 52, 53 greater than the inter-pixel distance d in the
respective dimensions, the transparent flexible substrate 22 or
transparent flexible cover 26 extensions defining a first transparent
tile area 20A on the first side of the pixel array 10, a second tile area
20B on the second side of the pixel array 10 opposite the first side, a
third transparent tile area 20C on the third side of the pixel array 10
adjacent to the first and second sides, a fourth tile area 20D on the
fourth side of the pixel array 10 opposite the third side and adjacent to
the first and second sides The first, second, third and fourth tile areas
20A, 20B, 20C, 20D do not include pixels 15, 15E and can have the same,
or different, sizes. In particular, the first and third transparent tile
areas 20A, 20C can extend the same distance from the pixel array 10.
Typically, the second and fourth tile areas 20B, 20D extend farther from
the pixel array 10 than the first and third transparent tile areas 20A,
20C as is discussed further below.

[0054]Referring back to FIGS. 1 and 2 and to FIG. 19 (in cross-section),
the first transparent tile area 20A of display tile 25 is disposed above
the second tile area 21B of the first neighboring display tile 25A so
that light 5 emitted from the second edge pixels 15B of the first
neighboring display tile 25A is transmitted through the first transparent
tile area 20A. The second tile area 20B is disposed below the first tile
area 21A of the second neighboring display tile 25B so that light 5
emitted from the second edge pixels 158 is transmitted through the first
transparent tile area 21A of the second neighboring tile 25B. Similarly,
in a second, orthogonal dimension, the third transparent tile edge 20C is
disposed above the fourth tile area 20D of the third neighboring display
tile 25C so that light emitted from the fourth edge pixels 15D of the
third neighboring display tile 25C is transmitted through the third
transparent the area 20C. The fourth tile area 20D is disposed below the
third transparent tile area 20C of the fourth neighboring display tile
25D so that light emitted from the fourth edge pixels 15D is transmitted
through the third transparent tile area of the fourth neighboring display
tile 251). Pixels 15 not on the edge emit light through the cover or
substrate of their respective display tiles only. Note that edge pixels
are those pixels that emit light through a neighboring display tile and
can include pixels in the interior of the pixel array, when adjacent to
other edge pixels. The pixels 15, 15A, 15B, 15E in the pixel arrays 10 of
the display tile 25 and the neighboring display tiles 25A, 25B, 25C, 25D
do not overlap, form a regular, two-dimensional pixel array, and are
separated by the inter-pixel distance d in each of the dimensions.

[0055]By continuing to dispose display tiles in rows and columns with an
overlying portion of one display tile over an underlying portion of a
neighboring display tile on one side of the display tile and a different
underlying portion of the display tile disposed under a different
neighboring tile on an opposite side of the display tile, the display of
the present invention can be scaled to an arbitrary size in either of the
two dimensions.

[0056]A flexible substrate or flexible cover is one in which the substrate
or cover is made in one physical configuration and employed in the
present invention in another physical configuration different from the
manufacturing configuration, for example made in a flat configuration in
which a display tile substrate surface is in a single plane and employed
in an at least partially curved configuration, for example in which the
tile surface is not in a single plane. A transparent substrate or cover
is a substrate or cover that transmits at least 50% of incident light in
the transparent tile areas (e.g. first and third transparent tile areas).
The remainder of the substrate or cover need not be transparent except
where light is emitted from the pixel array. The inter-pixel distance d
is the distance between pixels within a pixel array on a display tile and
the distance between the respective adjacent edge pixels of two separate
display tiles in a dimension. The inter-pixel distance d can be different
in the two dimensions.

[0057]Referring to FIG. 20, a transparent encapsulating adhesive 40 can be
used to adhere and align the cover and substrate of a display tile
together, e.g. substrate 22B and cover 26B. An optical adhesive 42 can be
used to adhere and align two display tiles together. The optical adhesive
42 in the light-emitting area of an edge pixel (e.g. 15B) is at least
partially transparent and preferably has a refractive index matched to
the index of the display tile cover 26 and substrate 22B. As used herein,
the transparent flexible substrate 22 and transparent flexible cover 26
include any adhesive or encapsulating material employed to adhere the
substrate and cover together or to adhere display tiles together, or any
electrodes or electrical conductors that are located outside the pixel
array of an overlapping portion of a display tile in the location of a
pixel in the two-dimensional pixel array. The entire assembly of the
display tile in the pixel locations outside the pixel array in the first
and third transparent tile areas is transparent with the exception of any
black matrix 28 material located between pixels, that is, in the
inter-pixel area.

[0058]As shown in FIG. 3, each display tile 25 includes a transparent
substrate 22 and a transparent cover 26 affixed to the transparent
substrate 22. A first electrode 12 is formed over the transparent
substrate 22, one or more layers 14 of light-emitting material are formed
over the first electrode 12, and a second electrode 16 is formed over the
one or more layers 14 of light-emitting material. In a bottom-emitter
embodiment of the present invention (as shown in FIG. 3), the first
electrode 12 can be transparent and the second electrode 16 can be
reflective. Alternatively, in a top-emitter configuration (not shown) the
first electrode 12 can be reflective and the second electrode 16 can be
transparent. A color filter 18 can be included on either side of the
substrate (for a bottom-emitter) or either side of the cover (for a
top-emitter) to filter light 5 emitted by the one or more layers 14 of
light-emitting material upon the application of a current through the one
or more layers 14 of light-emitting material by the electrodes 12, 16. A
black matrix material can he disposed between the pixels to absorb
ambient light or stray emitted light, as shown in FIG. 2. The light
emitted by the one or more layers 14 of light-emitting material can be
white or can be colored. The one or more layers 14 of light-emitting
material can be patterned or un-patterned; hence the color filters 18 are
optional.

[0059]Referring to FIG. 4, the first or second electrode 12, 16 is
patterned to form independently-controllable light-emitting pixels 15,
15E arranged in rows and columns in a regular, two-dimensional, pixel
array, the pixel array having edge pixels 15E located at the edge of the
pixel array, each pixel 15, 15E separated from a neighboring pixel 15,
15E by an inter-pixel distance d in each of the two dimensions. The
inter-pixel distance d in one dimension can be, but is not necessarily,
the same as the inter-pixel distance d in another dimension. The pixels
are located at grid points in a two-dimensional array, but not every grid
point need have a pixel. In particular, the edge pixels can have a
non-linear arrangement, as discussed further below. The pixels can be,
but are not necessarily, square. For clarity, the figures show square
pixels separated by a common inter-pixel distance d in both dimensions.
The substrate and cover of display tile 25 extend beyond the pixel array
on all four sides of the pixel array by a distance 52, 53 greater than
the inter-pixel distance d in the respective dimension and on the
respective side of the pixel array. As illustrated in the Figures, the
display tiles can, but do not necessarily, extend farther beyond an edge
pixel on one side of the pixel array (e.g. 52 for first and third tile
areas 20A, 20C) than on the opposite side (e.g. 53 for second and fourth
tile areas 20B, 20D). The farther extent of the display tile can be
located beneath a neighboring display tile.

[0060]Referring to FIG. 11, the tiled electro-luminescent display
apparatus in one embodiment further includes a black matrix material 28
formed on either side of the substrate or cover outside of the pixel
array as well as inside the pixel array between pixels 15.
Light-absorbing material 29 can also be disposed along the vertical edge
34 of the substrate and cover of a display tile. Such light-absorbing
material absorbs ambient light to improve the display contrast. The
light-absorbing material also absorbs stray light emitted by the pixels
and prevents light from escaping from the vertical edge of the display
tile substrate or cover. Desiccants 44 can be included to absorb
moisture.

[0061]In one embodiment of the present invention, (e.g. as shown in FIG.
11) the first transparent tile area or the third transparent tile area
has a vertical edge 34 that is located laterally between two pixels on
the corresponding neighboring tile.

[0062]In a related embodiment of the present invention in which the pixels
have a common width, the extent in the direction corresponding to the
pixel width of the display tile cover and substrate is matched to the
pixel 15 and black matrix 28 layout over the substrates 22, 22A (FIG.
12). As illustrated in FIG. 12, the substrate and cover 22, 26 of a
display tile 25 extends beyond a side of the pixel array a distance 50
greater than or equal to n(x+d) and less than or equal to n(x+d)+d, where
n is a positive integer, x is the pixel width in the direction the
substrate and cover extend beyond the side of the pixel array, and d is
the inter-pixel distance in the corresponding direction the substrate and
cover extend beyond the side of the pixel array. Such an arrangement will
locate the display tile cover and substrate edge above or below the black
matrix of a neighboring display tile (e.g. 25A). In this location, the
display tile cover and substrate edge (and any light leaking from the
display tile cover and substrate edge) are masked by the black matrix.
Note that, where substrate 22A and cover 26A of display the 25A is
disposed beneath display tile 25, its extent is not critical. However,
where substrate 22 and cover 26 of display tile 25 are disposed above (in
the direction of light emission) display tile 25A, the location of the
substrate 22 and cover 26 edges with respect to the black matrix 28 and
pixels 15, 15E of display tile 25A is important. In an alternative
arrangement, the edges of the cover and substrate of a display tile with
respect to the neighboring tile are disposed over a pixel so that light
escaping from the edge can be masked by the light 5 emitted from a pixel.

[0063]In order to provide power to pixels and facilitate their control, it
is necessary to electrically connect the pixel electrodes to controllers,
typically integrated circuits. The electrical connections and,
optionally, the controllers can be located on the same substrate as the
pixel electrodes, providing a high level of integration. However, the
electrical connections and controller can take space on the substrate
greater than the inter-pixel distance d between pixels. Referring back to
FIG. 4, in an embodiment of the present invention, the second tile area
20B and fourth tile area 20D of the display tile 25 substrate and cover
extend a greater distance 53 on two adjacent sides of the pixel array 10
than distance 52 on the two sides of the pixel array opposing the two
adjacent sides of the pixel array (i.e. first and third transparent tile
areas 20A, 20C). An extended electrode portion 60 of the first or second
electrodes 12, 16 extends a distance greater than the corresponding
inter-pixel distance d on the second and fourth tile areas and the first
or second electrodes 12, 16 do not extend a distance greater than the
corresponding inter-pixel distance d beyond the pixel array on the two
opposing sides of the pixel array. Hence, two adjacent sides of the
display tile extend farther from the pixel array and can have electrical
connections such as wires, and controllers, opaque or transparent,
disposed thereon. The opposite sides do not have to extend farther
because there are no electrical connections or controllers disposed on
the opposite sides. According to an embodiment of the present invention,
the second and fourth tile areas of a display tile are disposed beneath a
neighboring display tile, and the opposing side first and third tile
areas are disposed above a neighboring display tile on the opposite side.
In this configuration, therefore, at least some of the extended electrode
portion of a first display tile is disposed beneath the pixel array of a
second display tile, thus hiding the electrodes and controller from view.

[0064]FIG. 4 illustrates an embodiment having two controllers 30A, 30B and
extended electrode portions 60 located on the second and fourth tile
areas 20B, 20D of a display tile 25, one controller 30A controlling the
row electrodes (e.g. 12) and the other controller 30B controlling the
column electrodes (e.g. 16) in a passive-matrix control scheme. In FIG.
4, both the second and fourth tile areas 20B, 20D include a controller
30A or 30B and the respective electrodes controlled by the controllers.
In an alternative embodiment illustrated in FIG. 5, second tile area 20B
includes only the extended electrode portion 60A connecting pixel
electrodes 12 to a controller 30 disposed on fourth tile area 20D. Fourth
tile area 20D includes the extended electrode portion 60B connecting
pixel electrodes 16 to the controller 30. Controller 30 is thus connected
to extended electrode portions 60A and 60B, for example to row electrodes
and column electrodes 12, 16 to control pixels 15 and edge pixels 15E. In
an embodiment of the present invention, the one or more controllers are
chiplets. Referring to FIG. 21, chiplets 62 are small, unpackaged,
integrated circuits formed in or on a semiconductor substrate, such as
silicon, separate from the flexible transparent display tile substrate 22
or cover (typically glass or plastic), not shown. The chiplets 62 can be
printed on a display tile substrate 22 and connected to pixel electrodes
12, 16 and electrical connections with connection pads 68 using metal
wires and photolithographic techniques known in the art, for example as
disclosed in commonly assigned, currently pending U.S. patent application
Ser. No. 12/372,906, filed Feb. 18, 2009. Insulating and planarizing
layers 17 can be used to assist in the formation of electrical
connections. A layer 14 of light-emitting material is formed between the
pixel electrode 12, 16. In a further embodiment of the present invention,
a first display tile controller can be electrically connected to a second
display tile controller with a communication buss 64, (FIG. 6), for
example a serial buss. The controllers can provide passive-matrix control
to the pixels in each display tile (as illustrated in FIGS. 4 and 5), or
can provide active-matrix control.

[0065]FIG. 6 is a plan view of two overlapping display tiles according to
an embodiment of the present invention and corresponds to the arrangement
of FIG. 5 and the side view of FIG. 20. The underlying display tile 25B
is drawn with dashed lines to distinguish it from the overlying display
tile 25A. At least a portion of the second tile area of the underlying
display tile 25B is disposed beneath the pixel array of the overlying
display tile 25A. Each display tile 25A, 25B includes a controller 30A,
30B respectively. The controllers for each display tile can be
interconnected with a communication buss 64, for example a serial buss.
Alternatively, other busses, such as parallel busses, can be used. In
further embodiments of the present invention, many more display tiles can
be incorporated into a display apparatus. Referring to FIG. 7, a
simplified plan view of two display tiles 25 and 25B are shown, with a
portion of the display tile 25 (second tile area) shown with dashed lines
beneath a portion of the display tile 25B. Referring to FIG. 8, four
display tiles, 25, 25B, 25D, 25H, referred to as first, second, third,
and fourth, respectively, are shown aligned within a regular
two-dimensional pixel and tile structure with edge pixels 15E indicated.
Hence, the first and second display tiles 25 and 25B form a first row of
display tiles. The third and fourth display tiles 25D and 25H form a
second row of display tiles. First display tile 25 is shown at the
bottom, with second display tile 25B overlapping the right hand portion
(second tile area) of first display tile 25. Likewise, fourth display
tile 25H is shown overlapping the right hand portion (second tile area)
of third display tile 25D. Third display tile 25D overlaps a bottom
portion (fourth tile area) of first display tile 25 and a smaller portion
of second display tile 25B. Fourth display tile 25H is on the top. Hence,
according to an embodiment of the present invention, a portion of a third
display tile 25D (third tile area) is located above a portion of first
display tile 25 so that at least one edge pixel 15E on a different side
of the first display tile pixel array than the second display tile is
adjacent to at least one edge pixel 15E on a side of the third display
tile pixel array and separated from it by the corresponding inter-pixel
distance, and at least a portion of the adjacent first display edge
pixel(s) are located under the transparent substrate and cover of the
third display tile so that light emitted by the adjacent edge pixel(s) of
the first display tile 25 passes through the substrate and cover of the
third display tile 25D.

[0066]Furthermore, a portion of a fourth display tile 25H is located above
a portion of the second display tile 25B so that at least one edge pixel
on a different side of the second display tile pixel array than the first
display tile is adjacent to at least one edge pixel on a side of the
fourth display tile pixel array and separated from it by the
corresponding inter-pixel distance, and the adjacent second display edge
pixel(s) are located under at least a portion of the transparent
substrate and cover of the fourth display tile so that light emitted by
the adjacent edge pixel(s) of the second display tile passes through the
substrate and cover of the fourth display tile. A portion of the third
display tile is located beneath a portion of the fourth display tile so
that at least one edge pixel on a side of the third display tile pixel
array is adjacent to at least one edge pixel on a side of the fourth
display tile pixel array and separated from it by the corresponding
inter-pixel distance, and the transparent substrate and cover of the
fourth display tile are located over at least a portion of the adjacent
third display edge pixel(s) so that light emitted by the adjacent edge
pixel(s) of the third display tile passes through the substrate and cover
of the fourth display tile. As shown in FIG. 8, light is also emitted
through the substrate and cover of both the first and second display
tile.

[0067]FIG. 9 (and in comparison with FIG. 1) shows a further extension of
the tile structure to nine display tiles, a display tile 25 with eight
neighboring display tiles 25A, 25B, 25C, 25D, 25E, 25F, 25G, and 25H. In
this embodiment of the present invention, the tiled electro-luminescent
display apparatus further includes fifth and sixth neighboring display
tiles, 25E, and 25F. The first transparent tile area of the third
neighboring display tile 25C is disposed above the second tile area of
the fifth neighboring display tile 25E so that light emitted from the
second edge pixels of the fifth neighboring display tile 25E is
transmitted through the first transparent tile area of the third
neighboring display tile 25C. The third transparent tile area of the
first neighboring display tile 25A is disposed above the fourth tile area
of the fifth neighboring display tile 25E so that light emitted from the
fourth edge pixels of the fifth neighboring display tile 25E is
transmitted through the third transparent tile area of the first
neighboring tile 25A. The first transparent tile area of the sixth
neighboring display tile 25F is disposed above the second tile area of
the third neighboring display tile 25C so that light emitted from the
second edge pixels of the third neighboring display tile 25C is
transmitted through the first transparent tile area of the sixth
neighboring display tile 25E. The third transparent tile area of the
second neighboring display tile 25B is disposed above the fourth the area
of the sixth neighboring display tile 25F so that light emitted from the
fourth edge pixels of the sixth neighboring display tile 25F is
transmitted through the third transparent tile area of the second
neighboring tile 25B. Display tiles 25G, 25D, and 25I are similarly
arranged with respect to display tiles 25A, 25, and 25B as display tiles
25A, 25, and 25B are with respect to display tiles 25E, 25C, and 25F. The
pixels in the pixel arrays of the display tile and the nine display tiles
do not overlap, form a regular, two-dimensional pixel array, and are
separated by the respective inter-pixel distances in each of the
dimensions.

[0068]As illustrated in FIG. 8, edge pixels at the corners of the
bottom-most display tile where four display tiles overlap can emit light
through the substrate of the bottom display tile (25), the substrate and
cover of a neighboring display tile (25B) on one side, the substrate and
cover of a neighboring display tile (25D) on another, adjacent side, and
the substrate and cover of a the top display tile (25H). To reduce the
number of substrates and covers through which a pixel emits light,
according to a further embodiment of the present invention illustrated in
FIG. 10, the third and fourth display tiles (25D, 25H) are offset
laterally with respect to the first and second display tiles (25, 25B).
By offset is meant that display tiles aligned in rows are not likewise
aligned in columns with adjacent rows. However, the pixels of all of the
display tiles are still arranged in a regular two-dimensional array and
have a common inter-pixel distance in each dimension.

[0069]According to the present invention, the cover and substrate of the
display tiles are flexible. This flexibility permits the display tiles to
be made when the substrate and covers are flat, for example having a
surface in a single plane, simplifying the manufacturing process.
Referring back to FIG. 19, once made, the display tiles are flexed to
locate a first flat portion 24A of a first display tile 25 above a flat
portion 24C of a second display tile 25A. At the edge of the flat,
overlying portion 24A of display tile 25, a curved portion 24B of brings
the remaining flat portion 24C of the display tile 25 into the same plane
as the flat portion 24C of neighboring display tile 25A. Since the flat
portion 24C of display tile 25 is much larger than the flat portion 24A
of display tile 25, the display tile substrates will generally be located
in a common plane, with the exception of the smaller, flat portions 24A
that overlie neighboring display tiles and the curved portions 24B near
the edge of the display tiles. In an embodiment of the present invention,
the pixels of the larger flat portions (e.g. 24C) are parallel to a
viewing plane or are actually in a viewing plane. The smaller flat
portions (24A) can also be parallel to the same viewing plane, but
slightly offset in the viewing direction.

[0070]In one embodiment of the present invention, illustrated in the side
view of FIG. 13, the vertical length of a display tile edge in a single
plane is reduced by making the cover and substrate of the display tiles
have different sizes and be located in different planes so that the
substrate extends a distance beyond the edge of the cover or so that the
cover extends a distance beyond the edge of the substrate. In FIG. 13,
the cover 26A extends a distance 54A farther than the substrate 22A of
display tile 25A. In contrast, the substrate 22B of display tile 25B
extends a distance 54B farther than the cover 26B. By using
different-sized substrates and covers, light that leaks from either the
cover or edge is more widely dispersed and less visible.

[0071]In other embodiments of the present invention illustrated in FIGS.
14A and 14B, the edges of the cover and substrate of the display tiles 25
are jagged or stepped. In FIG. 14A, the edge forms a repeating pattern of
crenellations, and in FIG. 14B, the edge forms steps. Since long,
straight edges are readily perceived by the human visual system, using
jagged or stepped edges on one or more sides of a display tile reduces
the visibility of an edge in a tiled display apparatus. The changes in
edge direction can be mutually orthogonal and can be done in increments
of pixel widths, inter-pixel distance d, or the sum of the two.

[0072]As is known in the tiled-display art, visible seams between display
tiles are objectionable. These visible seams can result from irregular
pixel layout, non-uniform light output at the edges, changes in ambient
reflection at the display tile edges, and emitted-light leakage from the
tile edges. These difficulties are substantially mitigated by the present
invention. By using flexible transparent substrates and covers, one
display tile edge can be located beneath a neighboring tile. Furthermore,
the display tile portion located beneath a neighboring tile can be
increased in size to provide additional space for controllers and wire
routing. Therefore, in a bottom-emitter configuration, wires do not have
to be located between the pixels, thereby improving the aperture ratio
and the lifetime of a bottom-emitter electroluminescent display. By
employing area-emissive electroluminescent materials, the light output is
Lambertian and therefore the light emitted from the curved portion of the
display tile is indistinguishable from that emitted from flat portions.
By providing transparent substrates and covers, light from one display
tile can be emitted through the substrate and cover of an overlying
display tile, thereby enabling wide edges at the display tile perimeter.
These wide edges are easier to make and provide wider seals to prevent
the ingress of harmful moisture, either through the encapsulating
adhesive or through the substrate itself. Since flexible substrates
typically employ plastics, for example polyethylene teraphthalate (PET)
or polyethylene naphthalate (PEN), moisture ingress through the plastic
itself can be a problem. By providing a wide edge, the lifetime of the
device can be increased. Furthermore, flexible substrates and covers can
be very thin, for example 50 microns, compared to glass or other
inorganic substrates, as well as flexible. A thin substrate and cover
reduces the visibility of a display tile edge, especially when viewed at
an angle other than the normal to a flat substrate portion. Both the
reflection and refraction of ambient light and the reflection and
refraction of emitted light from a vertical edge are reduced.

[0073]According to a further embodiment of the present invention,
therefore, either or both of the substrate or cover has a thickness equal
to or less than the inter-pixel distance in one or both dimensions.
Alternatively, either or both of the substrate or cover have a thickness
equal to or less than the pixel width in at least one dimension. FIG. 20
illustrates the cases where the substrate is thinner than either of the
interpixel distance or the pixel width.

[0074]It is known in the art that a thin cover or substrate reduces the
loss of sharpness that can be found when employing diffusing layers to
extract trapped light from the pixels in an electroluminescent display.
According to another embodiment of the present invention, therefore, an
emitted-light-diffusing element can be optically integrated with the one
or more layers of light-emitting material. Referring to FIG. 15, an
emitted-light-diffusing element 66 is optically integrated with the one
or more layers 14 of light-emitting material in an OLED pixel. By
optically integrated with a layer is meant that any light trapped in the
layer is redirected by the emitted-light-diffusing element. By employing
such an emitted-light-diffusing element, any emitted light trapped within
the layers 14 of light-emitting material, electrodes 12, 16, substrate
22, or cover 26 can be emitted from the display tile, thereby improving
the efficiency of the display. Because the display tile cover and
substrate thickness can be much smaller than the inter-pixel distance d
or pixel width, the display tile sharpness is maintained.

[0075]It is a further advantage of the present invention that displays and
display tiles can be made at low cost. As is known in the OLED display
art, patterning light-emitting materials over a large substrate is
difficult and expensive. In yet another embodiment of the present
invention, therefore, a display tile can further include an array of
color filters located in correspondence with the pixels and a black
matrix located between the color filters, and wherein the one or more
layers of light-emitting material are unpatterned and emit white light to
form a full-color tiled display. Referring again to FIG. 15, a display
tile includes a substrate 22 on which is formed light-absorbing material
at the edge of the pixel array and black-matrix 28 and color-filter
elements 27 within the pixel array and in correspondence with the
patterned pixel-controlling electrodes 12 and common electrode 16. Over
the black-matrix 28 and color-filter elements 27 are located a
light-scattering layer forming an emitted-light-diffusing element 66.
This element 66 can be disposed in other locations, for example on either
side of the substrate or in optical contact with the electrode 16. An
OLED device including a first patterned electrode 12, one or more layers
of light-emitting material 14, and a second common electrode 16 are
formed over the emitted-light-diffusing element 66 or the black matrix 28
and color filters 27. An encapsulating cover 26 is adhered to the
substrate 22. A desiccant 44 can be employed within the encapsulating
cover 26 to absorb moisture.

[0076]In operation, an image, for example a digital image, is supplied by
an external image source through a connection buss connecting controllers
on each of a plurality of display tiles arranged as described above. The
controllers produce signals for driving the display tile pixels according
to the image information. The signals are transmitted onto row and column
electrodes formed over the display tile substrate causing the pixels to
emit light. In most of the display tile pixel areas, the pixels emit
light directly from the tiled display apparatus. However, any edge pixels
that are disposed beneath an overlying display tile will emit light
through the overlying display tile.

[0077]The present invention has the advantage of providing a scalable
display apparatus that can be arbitrarily extended. The edges can be
large and the display tiles can readily incorporate electrode and
electrical buss lines on the substrate, as well as controllers, without
reducing the aperture ratio of the display tiles in the pixel area. By
employing thin, flexible display substrates with electroluminescent
emitters, light emission from the pixels is uniform and the visibility of
the display tile seams greatly reduced. Furthermore, sharpness is
maintained even when light-diffusing elements are employed to improve
light output. Moreover, environmental protection for organic materials in
the one or more layers of light-emitting material is improved. By
employing chiplets with independent substrates (e.g. comprising
crystalline silicon) to control the display tiles, higher performance and
smaller size can be achieved than is found with conventional thin-film
circuitry. Flexible substrates, especially substrates including polymers,
typically have a low-process temperature threshold. Chiplets made
independently on a separate substrate and then printed onto a flexible
display tile substrate do not impose the same high temperature process
requirements as conventional thin-film circuitry, thereby enabling
high-performance circuits on flexible substrates with a high degree of
integration at relatively low cost. Such chiplets can have a thickness of
less than 100 microns or less than 20 microns, e.g. 12 microns.

[0078]FIG. 6 shows a diagram of a display apparatus constructed according
to an embodiment of the present invention. The display tiles were
constructed on PET substrates with moisture barrier layers and the same
material used for the encapsulating cover. Each tile had a 32×32
array of green-light emitting OLEDs. FIG. 16 shows two photographs of the
display apparatus in operation with two display tiles, overlapped as
described above. The lower image is that of a koala with the two display
tiles separated to indicate the image portion displayed on each display
tile. The upper image is that displayed by the combined display tile
structure. When the display tiles are carefully aligned, no seam is
visible at a designed viewing distance. Moreover, the light emitted by
the underlying edge pixels is not visibly different from other pixels.

[0079]FIG. 8 shows a diagram of a display apparatus constructed according
to another embodiment of the present invention with four display tiles
and one controller per display tile. This apparatus uses vertical black
light-absorbing material and demonstrates that the edge pixels at the
bottom of the four-display-tile stack are not visibly different from
other pixels in the pixel arrays. Some light leakage from the display
tiles can be seen under magnification at an angle to the normal, but at a
designed viewing distance, no display tile seam was visible and no
ambient light non-uniformity observed.

[0080]In an additional embodiment of the present invention, luminance
uniformity can be ensured by adjusting the source image data sent to each
tile so that the emissions from pixels with overlying tiles is
compensated for the light absorptions in the additional layers of
substrates, encapsulating covers, or adhesive.

[0081]The pixel array of the present invention forms a two-dimensional,
array. Each location in the array can include a pixel so that the pixels
form a rectangular grid. An additional advantage of the current
invention, however, is that the wider perimeter around the pixel array
can be used to create non-rectangular arrays of pixels such that the
tile-to-tile boundary between adjacent pixels will be more difficult to
detect visually. In this embodiment of the present invention,
light-emitting pixels in a display tile need not be located at every
pixel array location. Instead, the entire multi-tile display includes
pixels located at each point in the array. Within a single display tile,
the pixels can be arranged at some, but not all, of the array locations
in the two-dimensional grid. Edge pixels can be disposed in an irregular
pattern as discussed in U.S. Pat. No. 6,881,946. Arrays of pixels that
have non-straight sides hide variations in alignment and luminance. For
example, as shown in FIG. 17, a display tile can have a non-linear
saw-tooth pixel pattern on the edges of the pixel array. In this
embodiment of the present invention, a display tile 25 can have
electrodes 12 that are transparent and electrodes 16 that are reflective.
The overlapping portions of electrodes 12 and 16 form a two-dimensional
grid pattern of pixels 15, 15E that can be driven with a passive-matrix
control. Edge pixels 15E include all pixels that emit light through the
substrate and cover of a neighboring display tile and are not necessarily
on the outer-most row or column of the pixel array. The two-dimensional
tiling of six display tiles having jagged pixel edges is shown in FIG. 18
for display tiles 25A, 25B, 25C, 25D, 25E, 25F.

[0082]The flexible substrates and covers of the display tiles of the
present invention can include, for example, polymers such as PET or PEN.
Inorganic barrier layers can be formed as part of the substrates and
covers to inhibit the ingress of environmental contaminants, such as
moisture. Transparent, flexible covers can include thin-film layers
coated directly over or onto a substrate or can include separately
constructed films that are adhered to a substrate. Pixels can include,
for example, aluminum or silver reflective electrodes and metal oxide,
such as indium tin oxide, aluminum zinc oxide or indium zinc oxide,
transparent electrodes. Such conductors can be deposited on a substrate
by sputtering or evaporation and patterned with a mask or by
photolithography. Metal wires can also be formed from evaporated or
sputtered metal and patterned with masks or photolithography.
Alternatively, cured conductive inks can be employed to construct
electrical conductors. Light-emitting layers and charge-control layers
can include organic or inorganic materials as is known in the OLED art,
and can be deposited by evaporation and, if patterned, deposited through
a mask. Transparent adhesives and encapsulating adhesives are known in
the art.

[0083]The present invention can be employed in devices having a
multi-pixel infrastructure. In particular, the present invention can be
practiced with LED devices, either organic or inorganic, and is
particularly useful in information-display devices. In a preferred
embodiment, the present invention is employed in a tiled, flat-panel
array of OLED devices composed of small-molecule or polymeric OLEDs as
disclosed in, but not limited to U.S. Pat. No. 4,769,292, to Tang et al.,
and U.S. Pat. No. 5,061,569 to Van Slyke et al. Inorganic devices, for
example, employing quantum dots formed in a polycrystalline semiconductor
matrix (for example, as taught in U.S. Patent Application Publication No.
2007/0057263 by Kahen), and employing organic or inorganic charge-control
layers, or hybrid organic/inorganic devices can be employed. Many
combinations and variations of organic or inorganic light-emitting
displays can be used to fabricate such a device, including active-matrix
displays having a top-emitter architecture or having a bottom-emitter
architecture.

[0084]The invention has been described in detail with particular reference
to certain preferred embodiments thereof, but it will he understood that
variations and modifications can be effected within the spirit and scope
of the invention.